For many years, waste materials such as hazardous waste oil sludges from petroleum refineries were impounded in basins with little thought to their final disposition. These waste sludges occur as American Petroleum Institute (API) and Dissolved Air Flotation (DAF) separator bottoms, tank bottoms, spills, heat exchanger sludge, secondary emulsions, slop oil, and the like. Such waste materials have been classified by the Environmental Protection Agency as hazardous wastes, which therefore restricts their removal from the generation site for treatment and/or disposal. (See for example, Industry and EPA hazardous waste Nos. K048-K052, 40 CFR, Section 261.32, 1985). It is presently acceptable to land farm the wastes using especially developed strains of bacteria for decomposition of the oil. However, the heavy metal contents of the oil left behind in the soil presents potential groundwater and controlled run off contamination to the environment. Furthermore, the oil contained in the sludge is not recovered for reuse or recycling. Presently, some refineries recycle the waste and sludges to delayed cokers. However, the addition of the waste and sludges to the coke is deleterious to coke quality and lowers the value of the coke to a lower-priced fuel coke.
There is a need for the treatment of such hazardous waste materials with a high solids content which is capable of recovering the oil for reuse, such as a high-grade refinery feed, while producing nonhazardous waste materials suitable for conventional and safe disposal.
In U.S. Pat. No. 3,791,965 to Fitzsimons et al, the process disclosed is specific to re-refining of used petroleum products and not to waste sludges. The petroleum products treated by the Fitzsimons et al include crank case oil and transmission fluid collected at service stations and used cutting oils, rolling mill oils, and petroleum based cleaning solvents. The process is only capable of handling a raw feed stock of used liquid petroleum products with a viscosity ranging between that of mineral spirits to about SAE 60 weight oil, which is the method used for determining the viscosity of essentially solids-free liquids. The process handles only solids of small particle size and therefore, solids in excess 100 mesh (105 microns) must be removed prior to treating the feed stock.
The process disclosed in U.S. Pat. No. 3,923,643 to Lewis et al is intended for the exclusive purpose of the purification of used hydrocarbon lubricating oil, and is directed to the removal of suspended lead and other dispersed solids from used lubricating oil. As in Fitzsimons et al, this process is not capable of handling feed stocks containing more than minute amounts of solids or of producing nonhazardous waste by-products.
Additional prior art disclosing a process for cleaning low-solids-containing waste oil include U.S. Pat. No. 3,954,602 to Troesch et al. The process is specific to volatilizing the light oils and water only, and the organic solids residue removed by filtration from the remaining heavy oil is combusted for reheating oil treated in the process leaving no unburned matter. Other similar prior art for treatment of low solids waste oil include such patents as U.S. Pat. No. 4,512,878 to Reid et al for reclaiming used lubricating oils for reuse and U.S. Pat. No. 1,951,739 to C. J. Rodman et al for treating mineral hydrocarbon oil, especially those used in electrical apparatus.
This invention has as its purpose to provide for the treatment of hazardous waste oil sludge, which has essentially no upper limitation in solids content and with the solids particle size ranging from submicron to several inches (i.e. up to about six inches). Coarser materials can be treated by the process of this invention after size reduction by any suitable means such as grinding, crushing, pug mills, disintegrators, etc. The oil recovered is essentially the equivalent of cracker or cutter oil feed stock (based on the carbon chain contents, boiling point ranges, flash points, sulfur contents, etc.) and is suitable for further refining as in a cracking unit or as cutter oil feed stock. The water-free and oil-free solids are nonhazardous when tested in accordance with EPA toxicity test procedures, and therefore are suitable for disposal in a conventional sanitary landfill. Also, the waste water generated by the process of this invention is nonhazardous and therefore can be further treated in a conventional refinery water treatment system.